Many modern microcontroller have a cool feature: Pin Muxing. What it means is that I can ‘mux’ the pins for different purposes: such as I can use a SPI or I2C pin as GPIO (General Purpose Pin) or vice versa. In an ideal world, I would be able to ‘route’ or ‘mux’ pins freely around. In practice these ‘way switches’ are more or less limited.
In “Using the Reset Button on the Freedom Board as User Button” I muxed the FRDM-KL25Z reset pin as GPIO pin. The same approach can be used for muxing the NMI (Non-Maskable Interrupt) pin for the Freescale Kinetis devices. I’m showing it here how to do this with Processor Expert as this allows me to do this with a few mouse clicks.









